Bone Preparation Tool Kit and Associated Method

ABSTRACT

A prosthesis ( 20 ) for use in performing joint arthroplasty is provided. The prosthesis ( 20 ) is to be fitted to a long bone ( 3 ). The prosthesis includes a first body ( 22 ) having a first body articulating surface ( 24 ) defining a generally circular outer periphery ( 26 ) of the first body articulating surface ( 24 ). The first body ( 22 ) has a support surface ( 28 ) opposed to the articulating surface ( 24 ). The support surface ( 28 ) is adapted to receive the head of the long bone ( 3 ). The prosthesis ( 20 ) also includes a second body ( 30 ) operably associated with the first body ( 22 ). The second body ( 30 ) has a second body articulating surface ( 32 ) extending from a portion of the circular outer periphery ( 26 ) of the first body articulating surface ( 24 ). A tool kit for preparing a humerus to receive a prosthesis is also disclosed.

This application is a divisional of application Ser. No. 10/403,708,filed on Mar. 31, 2003 (Patent Application Publication No. US2004/0193277 A1). The disclosure of which is hereby totally incorporatedby reference in its entirety.

Cross reference is made to the following applications: DEP 755 entitled“ARTHROPLASTY SIZING GAGE”, DEP 756 entitled “ARTICULATING SURFACEREPLACEMENT PROSTHESIS”, DEP 789 entitled “MODULAR ARTICULATING SURFACEREPLACEMENT PROSTHESIS”, DEP 5041 entitled “ARTHROPLASTY INSTRUMENT ANDASSOCIATED METHOD”, and DEP 5052 entitled “PROSTHETIC IMPLANT, TRIAL ANDASSOCIATED METHOD” filed concurrently herewith which are incorporatedherein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of orthopaedics,and more particularly, to an implant for use in arthroplasty.

BACKGROUND OF THE INVENTION

The invention relates to implantable articles and methods for implantingsuch articles. More particularly, the invention relates to a boneprosthesis and a method for implanting the same.

There are known to exist many designs for and methods of implantingimplantable articles, such as bone prostheses. Such bone prosthesesinclude components of artificial joints, such as elbows, hips, knees andshoulders.

Early designs of implantable articles relied upon the use of cements toanchor the implant. However, the current trend is to use cements to alesser extent because of their tendency to lose adhesive properties overtime and the possibility that cement contributes to wear debris within ajoint.

Recently, implantable bone prostheses have been designed such that theyencourage the growth of hard bone tissue around the implant. Suchimplants are often implanted without cement and the bone grows aroundsurface irregularities, for example, porous structures on the implant.

One such implantable prosthesis is a shoulder prosthesis. During thelifetime of a patient it may be necessary to perform a total shoulderreplacement procedure on a patient as a result of, for example, diseaseor trauma, for example, disease from osteoarthritis or rheumatoidarthritis. Currently, most implantable shoulder prostheses are totalshoulder prostheses. In a total shoulder replacement procedure, ahumeral component having a head portion is utilized to replace thenatural head portion of the upper arm bone or humerus. The humeralcomponent typically has an elongated intramedullary stem, which isutilized to secure the humeral component to the patient's humerus. Insuch a total shoulder replacement procedure, the natural glenoid surfaceof the scapula is resurfaced or otherwise replaced with a glenoidcomponent that provides a bearing surface for the head portion of thehumeral component.

With the average age of patients requiring shoulder arthroplastydecreasing, device manufacturers are developing bone sparing implantsfor the initial treatment of degenerative arthritis. Surface replacementprostheses are being developed to replace the articulating surface ofthe proximal humerus with a minimal bone resection and minimaldisruption of the metaphysis and diaphysis. Current designs utilize asemi-spherical articular dome with a small stem for rotationalstability. The under surface of the articular head is alsosemi-spherical and mates with the spherically machined humeral head.

The need for a shoulder replacement procedure may be created by thepresence of one of a number of conditions. One such condition is thedeterioration of the patient's rotator cuff. Specifically, an intactrotator cuff stabilizes the humeral head in the glenoid fossa of ascapula during abduction of the arm. While it is stabilized in such amanner abduction of the arm causes the humeral head to translate only ashort distance in the superior direction (e.g. a few millimeters),whereby a space is maintained between the humeral head and the acromion.However, for patients with rotator cuff arthropathy, significantlygreater humeral excursion is observed.

Referring to FIG. 2, a healthy long bone in the form of humerus 1 isshown. The humerus 1 includes a healthy humeral head 2.

Referring now to FIG. 3, a diseased humerus 3 is shown. The diseasedhumerus 3 includes a diseased or flattened humeral head 4. Whereas thehealthy humeral head 2 of the healthy humerus 1 of FIG. 2 has agenerally hemispherical shape, the flattened humeral head 4 is quiteflat and only slightly domed.

Referring now to FIGS. 4, 5 and 6, a prior art prosthesis 5 is shown.Referring first to FIG. 4, the prosthesis 5 is shown installed on thediseased humerus 3. The prosthesis 5 is positioned over flattened heador bony defect 4. The prosthesis 5 includes a hollow generallyhemispherical cup 6. Extending distally from the interior of the cup 6is a generally conically shaped stem 7 that anchors the prosthesis 5into the humerus 3.

Referring now to FIGS. 5 and 6, the prosthesis 5 is shown implanted in ashoulder joint. As shown in FIG. 5, the humerus 3 is shown in a positionin which the arm is resting against the patient's torso. Articulatingsurface of the cup 6 of the prosthesis 5 is shown in contact with thescapula 7, the clavicle 8, and the acromion 9. As can be seen in FIG. 5,in this downward position of the humerus 3 the prosthesis 5 provides thearticulating surface of cup 6 in contact with the acromion 9, theclavicle 8, and the scapula 7 to provide for a acceptable artificialjoint in this position.

However, referring to FIG. 6, the humerus 3 is shown abducted in thedirection of arrow 10 such that the long bone or humeral centerline 11is at an angle α of about fifteen (15) degrees with the verticalcenterline 12. As can be seen in FIG. 6, on a slight abduction offifteen degrees, the acromion 9 is positioned outside the articulatingsurface 6 of the prosthesis 5 causing the acromion 9 to impinge upon thehumerus 3 causing great pain to the patient and severely limited motionof the humerus 3.

In particular, hyper-translation of the humeral head in the superiordirection is observed in patients with massive rotator cuff deficiency,thereby resulting in articulation between the superior surface of thehumeral head and both the inferior surface of the acromion and theacromioclavicular joint during abduction of the patient's arm. Sucharticulation between these components accelerates humeral articulardestruction and the erosion of the acromion and acromioclavicular joint.Moreover, such bone-to-bone contact is extremely painful for thepatient, thereby significantly limiting the patient's range of motion.In short, patients with massive rotator cuff tear and associatedglenohumeral arthritis, as is seen in cuff tear arthropathy, mayexperience severe shoulder pain, as well as reduced function of theshoulder.

In order to treat patients suffering from cuff tear arthropathy, anumber of prostheses and techniques utilizing existing prostheses haveheretofore been designed. For example, surgeons heretofore utilized arelatively large humeral head prosthesis in an attempt to completelyfill the shoulder joint space. It was believed that such use of a largeprosthesis would increase the efficiency of the deltoid muscle, therebyimproving motion of the shoulder. However, clinical experience has shownthat such use of a large humeral head prosthesis (overstuffs) theshoulder joint thereby increasing soft tissue tension, reducing jointrange of motion, and increasing shoulder pain. Moreover, such use of anoversized prosthetic head fails to resurface the area of the greatertubercle of the humerus, thereby allowing for bone-to-bone contactbetween the greater tubercle and the acromion during abduction of thepatient's arm.

A number of humeral head bipolar prostheses have also been utilized inan attempt to address the problems associated with cuff teararthropathy. It was believed that the relatively unstrained motion ofthe bipolar head would improve shoulder motion. However, heretoforedesigned bipolar prosthetic heads include relatively large offsets,thereby overstuffing the shoulder joint in a similar manner as describedabove. Moreover, scar tissue may form around the bipolar head thereby(freezing) the dual articulating motion of the prosthesis that has beenknown to create a large hemi arthroplasty that likewise overstuffs theshoulder joint. In addition, such bipolar prosthetic heads do not coverthe articulating surface between the greater tubercle and the acromion,thereby creating painful bone-to-bone contact between them.

Yet further, a number of techniques have heretofore been designed inwhich the relatively rough surface of the greater tubercle is resurfacedwith an osteotome or high speed burr. Although this approach results ina smoother tubercle contact surface, relatively painful bone-to-bonearticulating contact still occurs, thereby reducing the patient's rangeof motion.

More recently, the assignee of the applicant of the present inventionhas invented a method and apparatus for performing a shoulderreplacement procedure in a treatment of a cuff tear arthroplasty whichhas been filed in the U.S. Patent and Trademark Office under U.S.application Ser. No. 09/767,473 filed Jan. 23, 2001, hereby incorporatedin its entireties by reference in this application. This applicationprovides for a method and apparatus for treating cuff tear arthroplastyutilizing a total shoulder replacement prosthesis. This prosthesisincludes an artificial head as well as a stem that extends into a rimmedmedullary canal. Such a prosthesis is limited to use with a totalshoulder prosthesis and is not suitable for use with bone sparingimplants for the initial treatment of the degenerative arthritis.

What is needed, therefore, is a method and apparatus for performing bonesparing arthroplasty shoulder replacement surgery utilizing bone sparingimplants for the initial treatment of degenerative arthritis, which willbe useful in the treatment of cuff tear arthroplasty, which overcomesone or more of the aforementioned drawbacks. What is particularly-neededis a method and apparatus for performing a bone sparing implant shoulderprocedure that eliminates painful articulation between the greattubercle of the humerus and the acromion.

SUMMARY OF THE INVENTION

The present invention provides for an extended articulation resurfacingshoulder that provides a low-friction prosthetic bearing surface forarticulation between the greater tuberosity and the acromion. Such aprosthesis is utilized with a bone sparing minimal resection of aportion of the humeral head.

The present invention provides for an extended articulation resurfacingshoulder with superior/lateral flange for extended articulation into thecoracoacromial arch.

According to one embodiment of the present invention, a prosthesis foruse in performing joint arthroplasty is provided. The prosthesis is tobe fitted to a long bone. The prosthesis includes a first body having afirst body articulating surface defining a generally circular outerperiphery of the first body articulating surface. The first body has asupport surface opposed to first body articulating surface. The supportsurface is adapted to receive the head of the long bone. The prosthesisalso includes a second body operably associated with the first body. Thesecond body has a second body articulating surface extending from aportion of the circular outer periphery of the first body articulatingsurface.

According to another embodiment of the present invention, a tool kit forpreparing a humerus to receive a prosthesis is provided. The prosthesishas a first body having a first articulating surface and an opposedfirst support surface and has a second body having a second articulatingsurface and an opposed second support surface. The kit is used toprepare the humerus to receive the prosthesis. The tool kit includes areamer for preparing a first prepared surface on the humerus. The firstprepared surface receives the first support surface. The tool kit alsoincludes a bone cutting tool for preparing a second prepared surface onthe humerus. The second prepared surface receives the second supportsurface.

According to a further embodiment of the present invention, a method forperforming shoulder arthroplasty for an indication of rotator cuff teararthropathy is provided. The method includes the step of providing aprosthesis with a first body having a first articulating surface and anopposed first support surface and with a second body having a secondarticulating surface and an opposed second support surface. The methodalso includes the step of providing a tool kit for preparing a humerusfor receiving the prosthesis. The method includes the step of preparinga first prepared surface for cooperation with the first support surfacewith the tool kit. The method further includes the step of preparing asecond prepared surface for cooperation with the second support surfacewith the tool kit. The method also includes the step of implanting theprosthesis onto the first prepared surface and the second preparedsurface. The method also includes the step of providing an instrumentfor preparing a surface on a long bone, providing a plurality of trials,each of said trials being adapted to mate with the surface, selectingone of the plurality of trials, performing a trial reduction on said oneof said plurality of trials, determining if said one of said pluralityof trials is satisfactory, performing additional trial reductions asrequired, selecting one of a plurality of joint prostheses correspondingto one of said plurality of trials based upon the trial reductions, andimplanting the selected one prosthesis onto the long bone.

The technical advantage of the present invention includes the ability toprovide a low friction bearing surface between the greater tuberosityand the acromion. For example, according to one aspect of the presentinvention, a superior/lateral flange extends from a periphery of thehemispherical body of the prosthesis, which flange provides for extendedarticulation in the coracoacromial arch. Thus, the present inventionprovides a low friction bearing surface between the greater tuberosityand the acromion.

The technical advantages of the present invention further include theability to provide for an effective remedy for rotator cuff teararthropathy as part of a bone saving surgical procedure. For example,according to one aspect of the present invention, a prosthesis isprovided which includes a generally hollow hemispherical body whichmates with a slightly resected humeral head. Thus, the present inventionprovides for a surgical procedure with minimal bone loss.

Other technical advantages of the present invention will be readilyapparent to one skilled in the art from the following figures,descriptions and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of a extended head humeral prosthesis according tothe present invention shown in position implanted on a diseased humerus;

FIG. 2 is a plan view of a healthy humerus;

FIG. 3 is a plan view of a diseased humerus;

FIG. 4 is a plan view of a prior art humeral prosthesis;

FIG. 5 is a plan view of a prior art humeral prosthesis shown inposition implanted on a diseased humerus with the humerus shown in theretracted position;

FIG. 6 is a plan view of a prior art humeral prosthesis shown inposition implanted on a diseased humerus with the humerus shown in theextended position with the humerus impinged on the distal acromion;

FIG. 7 is an enlarged plan view of the extended head humeral prosthesisof FIG. 1;

FIG. 8 is a plan view of the extended head humeral prosthesis of FIGS. 1and 7 shown in position implanted on a diseased humerus and incooperation with the glenoid cavity shown in the retracted position;

FIG. 9 is a plan view of the extended head humeral prosthesis of FIGS. 1and 7 shown in position implanted on a diseased humerus and incooperation with the glenoid cavity shown in the abducted position freefrom impingement in the glenoid cavity;

FIG. 10 is an enlarged plan view of the extended head humeral prosthesisof FIGS. 1 and 7;

FIG. 11 is a cross sectional view of the extended head humeralprosthesis of FIG. 10;

FIG. 12 is an auxiliary view of the extended head humeral prosthesis ofFIG. 10 along the lines 12-12 in the direction of the arrows;

FIG. 13 is a plan view of a reamer assembly to prepare a humeral headfor the extended head humeral prosthesis of FIGS. 1 and 7;

FIG. 14 is a plan view, partially in cross section of a cutting guidefor use with a cutter to prepare a humeral head for the extended headhumeral prosthesis of FIGS. 1 and 7;

FIG. 15 is a top view of the cutting guide of FIG. 14;

FIG. 16 is plan view of a tool kit for preparing a humeral head for theextended head humeral prosthesis of FIGS. 1 and 7;

FIG. 17 is plan view of an end mill for preparing a humeral head for theextended head humeral prosthesis of FIGS. 1 and 7;

FIG. 18 is a plan view of another cutting guide for use with a cutter toprepare a humeral head for the extended head humeral prosthesis of FIGS.1 and 7;

FIG. 19 is a top view of the cutting guide of FIG. 18;

FIG. 20 is plan view of another tool kit for preparing a humeral headfor the extended head humeral prosthesis of FIGS. 1 and 7;

FIG. 21 is a plan view of another embodiment of a extended head humeralprosthesis according to the present invention;

FIG. 22 is a cross sectional view of the extended head humeralprosthesis of FIG. 21;

FIG. 23 is an auxiliary view of the extended head humeral prosthesis ofFIG. 21 along the lines 23-23 in the direction of the arrows;

FIG. 24 is a plan view of a tool kit for preparing a humeral head forthe extended head humeral prosthesis of FIGS. 21-23; and

FIG. 25 is a process flow chart for a method of performing shoulderarthroplasty surgery according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention and the advantages thereof are bestunderstood by referring to the following descriptions and drawings,wherein like numerals are used for like and corresponding parts of thedrawings.

Referring now to FIG. 7, an embodiment of the present invention is shownas prosthesis 20. The prosthesis 20 is used in performing bonepreserving joint arthroplasty. The prosthesis 20 is to be fitted to thehead of a long bone. For example, the long bone as shown in FIG. 7 is inthe form of humerus 3. The prosthesis 20 includes a first body 22 havingan articulating surface 24 defining a generally circular outer periphery26. The first body 22 also includes a second surface 28 opposed to thearticulating surface 24. The second surface 28 is adapted to receive thehead of the humerus 3.

The prosthesis 20 further includes a second body 30 operably associatedwith the first body 22. The second body 30 has a second bodyarticulating surface 32 extending from a portion 34 of the circularperiphery 26 of the first articulating surface 24. The second bodyarticulating surface 32 is adapted to prevent impingement of theacromion 9 (see FIG. 1) with the humerus 3 when the humerus 3 is in theabducted position (see FIG. 8).

While the prosthesis of the present invention may be secured to thehumerus by securing of the second surface 28 to the humerus and bonyingrowth there between, preferably and as shown in FIG. 7, theprosthesis 20 further includes a stem 36 operably associated with thefirst body 22 or the second body 30. As shown in FIG. 7, the stem 36 isassociated with the first body 22. The stem 36 is adapted to assist insecuring the prosthesis 20 to the humerus 3. As shown in FIG. 7, theprosthesis 20 is an integral or one-piece item. It should be appreciatedthat the prosthesis 20 may be modular. For example, the stem 36 may be aseparate component from the first body 22 or the second body 30.Likewise, the second body 30 may be a separate component from the firstbody 22.

As shown in FIG. 7, the first body 22 may have any shape capable forarticulating motion with the glenoid cavity (see FIG. 8), however,preferably the articulating surface 24 is generally convex. For example,and as shown in FIG. 7, the articulating surface 24 may be generallyhemispherical. Likewise, the second surface 28 may likewise be generallyhemispherical with the first body 22 being generally a hollowhemisphere. Similarly, the second body articulating surface 32 ispreferably convex and may have a generally spherical shape. Likewise,the second body second surface 38 may likewise be generally spherical.The second body 30 may thus also be generally a sector of a hollowsphere.

To provide for smooth motion of the humerus 3 through the abduction ofthe humerus 3 with respect to glenoid cavity 14 (see FIG. 8) boundaryportion 40 of the prosthesis 20 located between the second articulatingsurface 32 and the first articulating surface 24 where the secondarticulating surface 32 extends from the first articulating surface 24is generally smooth and continuous.

Referring now to FIG. 1, the prosthesis 20 of the present invention isshown installed in the humerus 3 with the adjacent bones of the clavicle8, scapula 7 and acromion 9 shown in position. As shown in FIG. 1, thehumerus 3 is abducted into an angle β with respect to vertical erectbody reference line 42. As can be seen in FIG. 3, the acromion 9 extendspast the boundary portion 40 separating the first body 22 of theprosthesis 20 from the second body 30 of the prosthesis 20. Thus, thesecond body articulating surface 32 is utilized to prevent the acromion9 from impinging on the humerus 3.

Referring now to FIGS. 8 and 9, the humerus 3 is again shown in positionwith the adjacent skeletal structure. In FIG. 8, the long bone orhumerus 3 is shown in position when the upper arm is in position againstthe torso. At the humeral position as shown in FIG. 8, the angle βbetween the vertical centerline 42 and humeral centerline 44 isrepresented by an angle ββ of approximately 15 degrees. In this positionof the humerus 3, it can be seen that the acromion 9 is in contact withthe first articulating surface 24 at acromion distal edge or outer edge13.

Referring now to FIG. 9, the humerus 3 is shown being abducted in thedirection of arrow 46 with the respective angle β equaling approximately60 degrees. In this abducted position, the outer edge 13 of the acromion9 is in a position such that the second articulating surface 32 of thesecond body 30 is used to provide a smooth articulating surface for theouter edge 13 of the acromion 9.

Referring now to FIG. 10, the prosthesis 20 is shown in greater detail.While the stem 36 of the prosthesis 20 may have any suitable shapecapable of providing support for the prosthesis 20 in the humerus 3,preferably, and as shown in FIG. 10, the stem 36 has a generalcylindrical shape. The first body 22 as shown in FIG. 10 may be in theform of a hollow hemisphere having a first longitudinal body centerline48. The stem 36 has a stem longitudinal centerline 50. As shown in FIG.10, the prosthesis 20 may be such that the first longitudinal bodycenterline 48 and the stem longitudinal centerline 50 are coincident.Such a configuration provides for a preferred central location of thestem 36.

Applicants have found that since the diseased humerus may becomeflattened around the humeral head, to provide adequate support to theprosthesis 20 in a diseased humerus, the support surface opposed to thearticulating surface 24 of the prosthesis 20 may include at least partof the second surface 28 to include a support surface 52 opposed to thefirst articulating surface 24. Preferably, for simplicity, the supportsurface may be generally planar.

To assist the prosthesis 20 in its strength and stability in the humerus3 and to promote the bony ingrowth around the prosthesis 20, theprosthesis 20 may include a porous coating 53 secured to, for example,the second surface 28 of the first body 22, the second surface 38 of thesecond body, the planar portion 52 of the second surface 28, as well ason the periphery of the stem 36. Any commercially available porouscoating will assist in the bony ingrowth of the prosthesis 20 to thehumerus 3. One particular porous coating is provided by the assignee ofthe instant application under the trade name POROCOAT™. Porous coatingmay be more fully understood by reference to U.S. Pat. No. 3,855,638 toPilliar, hereby incorporated in its entireties by reference.

As shown in FIG. 10, the circular outer periphery 26 of the articulatingsurface 24 of the first body 22 defines a first plane 54. Similarly, thesecond articulating surface 32 of the second body 30 defines a secondsurface periphery 56. The second surface periphery 56 defines a secondplane 58. The first plane 54 and the second plane 58 are non-coincident.The first plane 54 and the second plane 58, therefore, define an angleαα there between. As shown in FIG. 10, the angle αα is obtuse. While theangle αα may approach 180 degrees, the angle aa may likewise have arange of about 120 to 180 degrees. As shown in FIG. 20, the angle aa maybe around 138 degrees.

Referring now to FIGS. 11 and 12, the prosthesis 20 is shown in greaterdetail. As shown in FIG. 11, the stem 36 may be generally cylindricalhaving stem diameter SD and a length SL. The stem 36 may be tapered anddefined by an angle ω. The angle ω may be around 5 to 30 degrees.

The planar portion 52 of the prosthesis 20 may have any reasonablelocation with respect to the articulating surface 24 of the prosthesis20. The proper position of the planar portion 52 will depend on theflattening of the humeral head and how much corresponding amount ofresection may be required to the humeral head. The position of theplanar portion 52 with respect to the articulating surface 24 may bedefined by a flat dimension FD.

The hemispherical body 22 and second body 30 of the prosthesis 20 may bedefined with respect to a prosthetic center point 60. The articulatingsurface 24 may be defined by a radius R1 extending from center point 60the articulating surface 24. The second surface 28 may be defined by aradius R2 extending from the prosthetic center point 60 to the secondsurface 28. Similarly, the second articulating surface 32 may be definedby radius R4 from the prosthetic center point 60 to the secondarticulating surface 32. Similarly, the second surface of the secondbody 38 may be defined by radius R3 from the prosthetic center point 60to the second surface 28. For simplicity, the radii R1 and R4 may beidentical and for simplicity the radii R2 and R3 may be identical.

Referring now to FIG. 12, the underside of the prosthesis 20 is shown.

The prosthesis 20 may have any size compatible with the humerus.Preferably, and as shown in FIGS. 7 through 12, the prosthesis 20preferably blends with the periphery of the humerus. Thus, the size ofthe prosthesis 20 is governed generally by the size of the anatomicalhumerus.

The prosthesis 20 may be made of any suitable durable material that iscompatible with the human anatomy. For example, the prosthesis 20 may bemade of a ceramic, a plastic or a metal. If made of a metal, theprosthesis 20 may be made, for example, of a cobalt chromium alloy, atitanium alloy, or a stainless steel alloy.

Referring now to FIG. 16, an instrument in the form of, for example, areamer assembly 62 is shown for use in reaming, for example, thearticulating surface 24 of the prosthesis 20 of FIG. 7.

As shown in FIG. 13, the reamer assembly 62 includes a tool driver 64.The tool driver 64 includes a body 66 having a cutting tool adaptor 68and a drive adapter 70. The reamer assembly 62 also includes a reamer72. The reamer 72 is connected to the tool driver 64 by the cutting tooladapter 68. The reamer 72 may be a hemispherical grater type reamer.

Referring now to FIGS. 14 and 15, a bone cutting tool guide 74 is shown.The tool guide 74 may include a body 76 having a cylindrical bore 78 forreceiving a guide pin 80 and a elongated slot 82 for receiving a cuttingtool in the form of osteotome 84. The tool guide 74 is used to preparesurface 88 of humerus 3.

Referring now to FIG. 16, a tool kit 86 is shown for preparing a humerusto receive a prosthesis, for example, prosthesis 20 of FIGS. 7 through12.

As shown in FIGS. 7 through 12, the prosthesis 20 includes the firstbody 22 having the first articulating surface 24 and an opposed firstsurface support surface 28. The prosthesis 20 also includes the secondbody 30 that has the second articulating surface 32 and an opposedsecond support surface 38.

Referring again to FIG. 16, the kit 86 is used for preparing the firstsupport surface 28 and the second support surface 38. The tool kit 86 ofFIG. 16 includes the reamer 72 and may include the tool driver 64 toform the reamer assembly 62. The tool kit 86 further includes a bonecutting tool 84 for preparing a second prepared surface on the humerus 3for receiving the second support surface 38 of, for example, theprosthesis 20.

As shown in FIG. 15, the bone cutting tool 84 is used to prepare secondprepared surface 88 on the humerus 3. As shown in FIG. 15, the secondprepared surface 88 represents the inside surface of a cylinder. Such ashape on the humerus is necessary to accommodate the inner edge 90 ofthe second body 30 of the prosthesis 20. (See FIG. 11).

Preferably and as shown in FIG. 16, the kit 86 further includes the bonecutting tool guide 74 for guiding the osteotome 84 through the elongatedslot 82 of the bone cutting tool guide 74. The osteotome 84 may bestruck with mallet 96.

Referring now to FIG. 10, it should be appreciated that if the angle ααapproaches 180 degrees, it may be possible to provide for the reaming ofthe humerus with a reamer assembly 62 (see FIG. 13) and merely pivot thereamer assembly 62 to form a contour for both the second surfaces 28 and38.

It should be appreciated, however, as the angle αα moves from 180degrees to something less, for example, 140 degrees the inner edge 90 ofsecond body 30 of prosthesis 20 (see FIG. 11) moves closer to the stemcenterline 50 such that a generally hemispherical grater-type reamersuch as that of FIG. 13 may not be appropriate to prepare thehemispherical head of the humerus. Therefore, the guide 74 of the kit 86provides for a surface 88 that is generally cylindrical to permit thecorner 90 of the prosthesis 20 to be fully seated into the humerus.

It should be appreciated that the bone cutting tool necessary to preparethe humerus may include a drill, a reamer, a broach, a saw or anosteotome.

Referring now to FIGS. 17 through 20, an alternate tool kit 186 forpreparing a humerus is shown. Referring first to FIG. 17, end mill 192is shown. End mill 192 may be any commercially available milling cuttercapable of end cutting.

Referring now to FIGS. 18 and 19, a bone cutting tool guide 174 is shownfor use with the end mill 192 of FIG. 17. The guide 174 includes a body176. The body 176 includes an opening 178 for cooperation with locationpin 180. The location pin 180 is used to orient the guide 174 withrespect to the humerus 3. The guide 174 further defines a plurality ofslots 182 formed in the body 176.

Referring to FIG. 19, the slots 182 extend an angle θθ about theperiphery of concave inner surface 194 of the guide 174. The slots 182are aligned somewhat parallel to each other and slightly spaced apart.The slots 182 are close enough to minimize the amount of material notcovered by the slots but far enough apart to provide enough strength tothe guide 174, particularly around the slots 182.

Referring now to FIG. 20, the kit 186 is shown. The kit 186 includesreamer assembly 162 for preparing the first prepared surface on thehumerus. The reamer assembly 162 is similar to reamer assembly 62 ofFIG. 13 and includes a tool driver 164 similar to the tool driver 64 ofFIG. 13 as well as a grater type hemispherical reamer 172 similar to thereamer 72 of the reamer assembly 62 of FIG. 13. The kit 20 furtherincludes end mill 192 as well as an osteotome 184 similar to osteotome84 of the kit 86 of FIG. 16. The osteotome 184 serves to remove thematerial remaining after the end mill 192 removes materials in alignmentwith the slots 182 of the guide 174. Preferably and as shown in FIG. 20,the kit 186 may further include the guide 174. Further, the kit 20 mayinclude a surgical mallet 196. The surgical mallet 196 is used to strikethe osteotome 184.

Referring now to FIGS. 21, 22 and 23, an alternate embodiment of thepresent invention is shown as prosthesis 120. Prosthesis 120 is similarto prosthesis 20 of FIGS. 7 through 12 except that prosthesis 120 isdesigned to take into consideration the limit in installing theprosthesis onto the prepared humeral head. Mainly, the prosthesis 120takes into consideration the inability to clear the edge 90 of theprosthesis 20 when utilizing a spherically shaped humeral head.

Referring now to FIG. 21, the prosthesis 120 includes a first body 122having a hemispherical articulating surface 124 and an opposed concavearcuate surface 128. The first body 122 also has a planar portion 152opposing the articulating surface 124. The prosthesis 120 furtherincludes a tapered cylindrical stem 136 extending inwardly from theplanar portion 152 of the first body 122. The prosthesis 120 furtherincludes a second body 130 extending from circular outer periphery 126of the first body 122. A boundary portion 140 is located between thefirst body 122 and the second body 130 and is preferably smooth andcontinuous. Unlike the prosthesis 20, the second body 130 of theprosthesis 120 has an opposed surface in the form of a cylindrical innerperiphery 138. The cylindrical periphery 138 is designed to matingly fitwith the cylindrical surface prepared on the humeral head.

Referring now to FIG. 22, the cylindrical periphery 138 is shown ingreater detail. The cylindrical periphery 138 is defined by a radiusR.sub.c extending from stem centerline 150.

Referring now to FIG. 23, another view of the cylindrical periphery 135of the prosthesis 120 is shown. The cylindrical periphery 135 is againdefined by a radius R.sub.c from stem centerline 150.

Referring now to FIG. 24, an alternate tool kit is shown as tool kit286. The tool kit 286 is used to prepare a humerus for the prosthesis ofthe present invention. The tool kit 286 includes a reamer assembly 262similar to the reamer assembly 162 of the kit 186 of FIG. 20. The toolkit 286 further includes a cylindrical end cutting reamer 292 having acylindrical cutting surface 297 and a guiding surface 298. The kit 286further includes a guide 274 for guiding the cylindrical reamer 292 in aproper path to properly prepare the humerus. The guide 274 includes abody 276 defining an opening 278 for cooperation with location pin 280,which is utilized to properly position the guide 274 on the humerus. Thebody 276 of the guide 274 further includes an arcuate elongated slot 282that cooperates with the guiding surface 298 of the reamer 292 to guidethe reamer along a proper path. The arcuate slot 282 is defined by anincluded angle θθθ.

Referring now FIG. 25, an alternate embodiment of the present inventionis shown as surgical method 300. The method 300 includes the first step302 of providing a prosthesis with a first body having a firstarticulating surface and an opposed first support surface and with asecond body having a second articulating surface and an opposed secondsupport surface. The method 300 further includes a second step 304providing a tool kit for preparing a humerus for receiving theprosthesis. The method 300 further includes a third step 306 ofpreparing a first prepared surface for cooperation with the firstsupport surface with the tool kit. The method 300 also includes a fourthstep 308 of preparing a second prepared surface for cooperation with thesecond support surface with the tool kit. The method 300 furtherincludes a fifth step 310 of implanting the prosthesis onto the firstprepared surface and the second prepared surface.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made therein without departing from the spirit andscope of the present invention as defined by the appended claims.

1. A tool kit for preparing a humerus to receive a prosthesis with afirst body having a first articulating surface and an opposed firstsupport surface and with a second body having a second articulatingsurface and an opposed second support surface, said kit for preparingthe humerus for receiving the prosthesis, said tool kit comprising: areamer for preparing a first prepared surface on the humerus forreceiving the first support surface; and a bone cutting tool forpreparing a second prepared surface on the humerus for receiving thesecond support surface.
 2. The tool kit of claim 1, wherein said bonecutting tool comprises one of a drill, a reamer, a broach, a saw and anosteotome.
 3. The tool kit of claim 2: wherein said bone cutting toolcomprises an end cutting reamer for preparing a plurality of channels inthe humerus; and further comprising a guide for controlling the positionand depth of said reamer.
 4. The tool kit of claim 1, further comprisinga guide for controlling the position of said bone cutting tool.
 5. Amethod of performing shoulder arthroplasty for an indication of rotatorcuff tear arthropathy comprising the steps of: providing a prosthesiswith a first body having a first articulating surface and an opposedfirst support surface and with a second body having a secondarticulating surface and an opposed second support surface; providing atool kit for preparing a humerus for receiving the prosthesis; preparinga first prepared surface for cooperation with the first support surfacewith the tool kit; preparing a second prepared surface for cooperationwith the second support surface with the tool kit; and implanting theprosthesis onto the first prepared surface and the second preparedsurface.